Minimally invasive endoscopic surgical procedures have become increasingly widespread in view of the reduced trauma for patients, and their highly cost-effective nature. For such procedures, a trocar assembly is typically employed for effecting penetration of the wall of a body cavity of the patient. A typical trocar assembly includes an outer tubular cannula, and an inner tissue-piercing obturator having a puncturing tip. For use, the trocar assembly is positioned so that the obturator can be advanced to form an opening in the wall of the body cavity with the puncturing tip, and the cannula thereafter inserted through the opening. The obturator is then removed from within the cannula, with the cannula thereafter providing access for insertion of surgical instruments and other devices related to the surgical procedure to be performed.
Many trocar assemblies have a retractable or removable shield that can cover the puncturing tip of the obturator, thus covering the tissue-piercing portion of the assembly. When the trocar assembly is positioned for puncturing the body cavity of a patient, the shield can be retracted to expose the puncturing tip to pierce the wall of the body cavity. Once the body cavity has been pierced, the shield re-covers the puncturing tip of the obturator. For example, in abdominal surgery, when the peritoneal cavity is reached, the shield covers the puncturing tip of the obturator.
Use of ultrasonic surgical instruments is also becoming increasingly widespread by virtue of the unique performance characteristics of such devices. Depending upon specific instrument configuration and operational parameters, such devices can provide substantially simultaneous cutting of tissue and hemostasis, again desirably minimizing patient trauma.
U.S. Pat. No. 5,449,370, hereby incorporated by reference, discloses an ultrasonic trocar assembly including an ultrasonic obturator configured to effect ultrasonic penetration of the wall of a body cavity for subsequent introduction of a tubular cannula of the trocar assembly. The obturator of the trocar assembly is provided with a blunt or rounded tip for minimizing patient trauma attendant to penetration of the body cavity. When the obturator penetrates the tissue of a patient, a feedback mechanism shuts off or reduces the ultrasonic energy delivered to the obturator.
The present invention is directed to an interlock or braking mechanism that mechanically dampens the ultrasonic energy delivered to a transmission component.